Method for producing organosiliconhalides



' 1945- c. E. REED ETAL METHOD FOR PRODUCING ORGANQ-SILICONHALIDES FiledSept. 27, 1945 2 Shets-Sheet 1 1 Inventors:

Ch EITIQS E. Reed,

Jerome T Coe,

Their Attorney- Nov. 27, 1945. c REED ET AL 2,389,9 3l

METHOD FOR PRODUCING ORGANO-SILICONHALIDES Filed Sept. 27, 1945 2Sheets-Sheet 2 9 .95 12 as :26): 96 v 55 g3 '60 V v I v 62 ii 91 v 1 T V82 97 63 v 193-- v 94 l 1 67' f --6/ v V 144 as me P '2' 1/8 104 -10;//Z/ 128 a 1 l L --1a4 122 e e el (L mt V Y W V I V 124 125 m5 111 "2//3 114 H T /30 13/ /29 Inventors:

Their Attorney.

Patented Nov. 27, 1945 METHOD FOR PRODUCING OBGANO- SILICONHALIDESCharles E. Reed, Schenectady, and Jerome T. Coe,

Fort Schuyler, N. Y., asslznors to General Electric Company, acorporation of New York Application September 27, 1943, Serial No.504,674

11 Claims.

The present invention relates to a method for the preparation oforgano-silicon compounds. It is particularly concerned with theproduction of organo-silicon halides from powdered or finely dividedsilicon and hydrocarbon halides.

The preparation of organo-silicon halides by contacting hydrocarbonhalides with a mass of silicon is described and broadly claimed in thecopending application of Eugene G, Rochow, Serial No. 412,459, filedSeptember 26, 1941 and assigned to the same assignee as the presentinvention. The products of the reaction may comprise any or all of thevarious organo-silicon halides of the general formula RnSiXa-n wherein Rrepresents an alkyl, aryl, aralkyl, r alkaryl radical, X representsahalogen atom, and n is equal to 1, 2, or 3, along with various othersilicon compounds such as silicon tetrahalide, tetraorgano silane andmono-organo dihalogenosilane. The reaction between the silicon mass andthe hydrocarbon halides is highly exothermic and unless the heat ofreaction is promptly removed,

the reaction temperature will rise at an ever accelerating rate. Theimmediate result of an uncontrolled increase in the temperature of thereaction mass is the formation of more of the less desirable triandtetra-halides and an undesirable deposition of carbon on the siliconmass.

. of a stationary mass of the silicon reactant at a rate suflicient tocontrol the reaction temperature is extremely diflicult.

The present invention is concerned primarily with a method for carryingout the reaction between a hydrocarbon halide and silicon powder wherebythe temperature of the silicon reactant may be readily controlled toproduce the desired reaction products. The nature of the invention willbe readily understood from the following description thereof taken inconnection with the accompanying drawings wherein Figure 1diagrammatically shows one form of apparatus in which the method may beoperated, and Figures 2-5 show various modified apparatus involving theoperating principles of the apparatus shown in Fig. l.

Briefly described, the present invention in its preferred form comprisescontacting a hydrocarbon halide with the silicon reactant infinelydivlded or powdered form under conditions 0! violent agitationwith provision for removing hot, unreacted silicon powder from thereaction zone, cooling it, and reinjecting cooled powder into thereaction zone in such quantity as to absorb the high heat of reactionand efiect precis control over the reaction temperature. The movementand agitation of the powder in the reaction zone and the circulation ofthe powder through a cooling zone is accomplished by non-mechanical,fluid-dynamical means.

The invention will be described with particular reference to thepreparation of methyl silicon chlorides by reacting methyl chloride withsilicon. It is to be understood however that it is not limited theretobut is broadly applicable to the reaction of powdered silicon with otherorganic compounds such as other hydrocarbon halides or alcohols. Thus itmay be'employed in the preparation of other alkyl silicon halides, (e.g. ethyl, propyl, butyl, amyl, isoamyl, hexyl, etc., silicon halides),the aryl silicon halides (e. g., phenyl silicon halides, etc.), thearyl-substituted aliphatic silicon halides (e. g., phenylethyl siliconhalides, etc), and the aliphatic-substituted aryl silicon halides (e.g., tolyl silicon halides, etc), mixed silicon halides (e. g methylethyl silicon halides, ethyl phenyl silicon halides, etc.) alkylenesilicon halides (e. g. the ethylene silicon chlorides described andclaimed in copending application Serial No. 433,328 Patnode andSchlessler, filed March 4, 1942, and assigned to the same assignee asthe present invention) and in the production of organo silicates such asmethyl silicate from methyl alcohol and silicon powder. It is to beunderstood that the powdered silicon reactant may be pure silicon or apowdered mixture (or alloy) of silicon and a catalyst or solid diluent,all of which are intended to be covered by the terms silicon powder or"powdered silicon as used hereinafter and in the appended claims.

Referring to Fig. 1, a reactive gas, such as methyl chloride isintroduced into the apparatus through inlet pipe I, flows upward andmeets a stream of silicon p wder flowing down inclined leg 2. The gasfluldizes the powder and the resultant mixture ascends through uprightreactor tube or vessel 3 to a separatory chamber or head 4 having alarger cross-sectional area than tubular reactor 3. In separatorychamber 4,

most of the unreacted slliconpowder is disengaged irOm the unreactedmethyl chloride and the gaseous products of reaction formed in reactor 3(and to'some extent in separatory chamher 4) since the gas velocity inchamber 4 is almost negligible as compared with the gas velocity inreactor 3. A bame 5 may be provided to aid in' the separation. 11desired, a more eflicient separation of the powder may be obtained bydesigning this portion of the apparatus along the hues of a cycloneseparator. Tne separated powder collecting on the inclined floor b ofchamnet 4 flows into vertical return pipe I, the lower end of which isconnected to inchned leg 2. Pipe I functions as a coohng chamber orvessel for the dissipation of the heat or reaction absorbed by thesilicon powder. In operation of the apparatus, pipe 1 down to valve 8 isordinarily nlled with a relatively solid mass of powder having a bulkdensity or 65-80 pounds per cubic feet and control over the downwardflow of this powder is exercised by means of valve 8. The velocity ofdownward flow of powder may be observed through sight glass 9. Thefluidized mixture of powder and gas ascending reaction tube 3 has a bulkdensity varying from 3-40 pounds per cubic ioot depending upon the rateat which methyl chloride enters through I relative to the rate at whichpowder is throttled through valve 8 and on the density of the gas phaseunder any particular set of conditions. The pressure drop measuredacross reactor tube 3 by means of pressure taps w is due almost entirelyto the weight of fluidized silicon powder flowing up 3, the irictiondrop due to fiow being almost negligible compared to this potentialhead. Since the eiiective pressure produced by the column of powderabove valve 8 exceeds the pressure at the bottom of 3, relatively highbulk density powder flows down tube 1 and powder dispersed in gas to alower bulk density flows up tube 3. The result is a continuouscirculation of silicon powder through a closed cycle comprising areaction chamber, a separator chamber and a cooling chamber. Practicallythe entire, quantity of methyl chloride admitted through I flows up tube3 due to the relatively lower density of the powder contained thereinand hence reaction occurs largely in this zone. As was previouslystated, a certain amount of reaction may in some cases occur in chamber4. Reaction products carrying small quantities of unseparated siliconpowder fiow from the reaction head through conduit II and enter cycloneseparator I! where a major portion of any silicon powder entrained isdropped out into receiver l3. From cyclone separator I! the reactionprod- ,ucts flow through transfer line l4 into filter l5 where residualfine silicon dust is removed by filter cloth IS. The reaction productsfinally pass to condenser ll provided with cooling coils l3 where theproducts are wholly or partially condensed. The condensate is collectedin receiving drum [9. Any non-condensible vapors are vented from thesystem through exhaust line 23. The downward flow of powder throughreturn tube I may be aided by injection of small quantities of methylchloride or other suitable gas, such as nitrogen, through lines 2|. Suchgas also serves to purge the powder oi reaction products and therebypermits the use of much lower cooling temperatures in this tube withoutcondensation of any entrained product vaporto liquid, which condensationmight produce a pasty condition that would interfere seriously with theflow of an otherwise fluid powder.

under subor super-atmospheric pressure either up to or includingcondenser l1 and receiver II by means of valves 22 or 23.

Reaction tube 3, its contents, and reactor head 4 are initially raisedto reaction temperature for example by means or electric heatingelements (not shown) wound around reactor 3 and inserted into or woundaround head 4 and the chemical reaction in these portions of theapparatus may be conducted with no gain or loss of heat through thewalls. As the weight ratio of the silicon powder to methyl chlorideflowing through tube 3 is, for example, of the order of one hundred toone, the temperature rise in this section of the apparatus resultingfrom liberation of reaction heat is very moderate and can be almostcompletely eliminated by suitable modifications in design which makepossible the unique combination of an adiabatic reactor operatingsubstantially isothermally. By this arrangement, the heat of reaction isremoved from the reaction chamber in very positive fashion at acontrolled temperature level by means of a circulating powder which isitself one of the reactants. This type of apparatus also permits heat tobe removed as sensible heat in an inert gas mixed in with the methylchloride or a combination of the two methods may be employed. Thetemperature of silicon powder flowing to inclined pipe 2 is measured bythermocouple 24. The thermocouple can also act as the detecting elementfor a controller (not shown) which will control wall temperatures intube I and hence the quantity of reaction heat dissipated from the sys-4o normally closed by cap 21.

One of the outstanding advantages of carrying out the reaction betweensilicon and methyl chloride in this manner resides in the fact that thepositive temperature control and dissipation of reaction heat therebyobtained makes practical the construction of large capacity units whichmay be operated with highly reactive, finely powdered silicon at highefficiency with low labor costs. The intense turbulence in reactor tube3 provides an unusually effective contact between a silicon powder andgas desirable in a heterogeneous reaction and minimizes lateraltemperature gradients and hot spots. Since it is unnecessary in thistype of apparatus to remove heat directly from the reaction zone, thereare no theoretical limits on the diameter of the reaction vesselcomprising this zone. The sensible heat from the circulating powder isabsorbed in a separate heat exchanger I in which the temperature of thecooling surface may be much lower than if it were in the reactor properwhere too cool a surface will lower reaction rate to uneconomicallevels. The rapid circulation and agitation of powder insures the sametreatment for every grain of powder at every stage of the reaction andunlike a static bed reactor where the state of the silicon powderunavoidably varies from top to bottom, optimum conditions for the entirecharge may be maintained at all times in the reaction zone.

It is also possible to increase the rate of reaction in apparatus of thetype disclosed herein by operating under pressure without experiencingany localized overheating. When pressure operation is employed, it isalso possible to lower The system may be reaction temperatures and atthe same time ob tain equal or higher yields of dimethyldichlorosilane.Operation under only moderate pressure. for example, a pressure of 80lbs., presents the further advantage of permitting total condensation ofthe reaction products including any unreacted methylchloride at ordinarycooling water temperatures, followed by a low cost stripping operationand recirculation of the unreacted methyl chloride.

The exact design and operation of the methyl chloride-silicon converterand the use therewith of means for recovering and recirculatingunreacted methyl chloride is dependent on economic considerations. Thereactor may be designed for high conversion per pass of methyl chlorideby provision for an increased time of contact of the methyl chloridewith silicon (e. g., by use of an elongated reaction chamber). Suchincreased conversion per pass will be realized however at the expense oflowered production capacity per unit volume of reactor due to the loweraverage rate of reaction resulting from the lower average partialpressure of methyl chloride. On the other hand, the use of a shorterreactor tube will result in a lower conversion per pass and higheraverage rate of production of methylchlorosllanes per unit volume ofreactor, but will require a larger recovery system and a greater methylchloride recirculation. Hence, the optimum size of the apparatus willdepend on the desired products, cost of various pieces of equipment, andoperation thereon For small scale production, exceptionally good resultshave been obtained with fluid dynamic apparatus in which the reactiontube 3 was 1.5 inches diameter and 32 feet long, the cooling return tubeI two inches in diameter and 29 feet long, and the separatory head 4sixteen inches in diameter. The distance from powder return tubeentrance to top of separatory chamber along floor 8 was 3.0 feet. Thereactor, cyclone separator, and filter were operated under a pressure of40-50 lbs. gage. Methyl chloride at room temperature was fed intoreactor tube 3 through entrance tube I at a rate of 12-15 lbs/hr. Theapparatus was charged with a mixture of 90 per cent silicon and per centcopper fired for two hours at 1050 C. and thereafter crushed to 60 -100mesh. The temperature of powder returning through tube 2 as measured onthermocouple 24 was 330-340 C. and temperature of powder enteringreaction head 4 as measured by thermocouple 28 was 360-370 C. Thesetemperatures are believed to represent very closely the actual reactionzone temperatures since the violence of the turbulence throughout thereaction zon and in the vicinity of the thermocouples results in athorough mixing of the powder and positively eliminates the existence ofany local hot spots. Pressure on the system was maintained by throttlevalve 22 and the product was collected from water condenser H inreceiver IS. The reactor was charged with powder at the start of the runand several times during the run through pipe II. All lines, cyclones,filters, etc., were maintained at a sufllciently high temperature toprevent premature liquefaction of any of the reaction products. Over a24-hour period the average rate of production of total reaction productwas 9.4 lbs/hr. and the average distillation analysis of the productshowed it to contain about 57 per cent-dimethyldichlorosilane. Theaverage dimethyldichlorosilane content of the prodnote obtained fromstatic bed reactorsis generally considerably less than 50 per cent.

A convenient basis for comparison of the productlon capacity ofdlflerent types of reactors is the index:' lbs. of product produced perhr, per

cubic it. of superficial reactor volume. This value for the 24 hr, runoutlined above is 20.9. It may be compared with that of 0.57 for astatic bed reactor 4 internal diameter and 8 ft. long and 3.6 for astatic bed reactor 1.5" internal diameter and 6 ft. long. The use oflonger static reactor tubes would result in a decrease in these valuesdue to the overall lower partial pressure of methyl chloride.

It is obvious that the output of apparatus of this invention is roughlyproportional to the effective reactor volume. Since the diameter of thereaction tube and the operating pressure may both be increased withoutlosing control over reaction temperature, single units of large capacityand low operating cost may be used. The maximum size, particularlythemaximum diameter, of static reactor tubes is definitely limited dueto the problem of controlling the reaction temperatures within suchtubes.

In Figure 2 there is shown apparatus comprising two of the fluid-dynamicreactors of the type shown in Fig. 1 operating in cascade. More than tworeactor units may also be operated in this manner. In the operation ofthis type of apparatus as applied for example to two units, unit No. 1preferably operates at a higher pressure than unit No. 2. For example,No. 1 may operate at 50 lbs. bottom pressure and 45 lbs. head pressurean No. 2 at 35 lbs. bottom pressure and 30 lbs. head pressure, so thatit is possible for a gaseous dispersion of powder to flow from the headof No. 1 at 45 lbs. to the head of No. 2 at 30 lbs. In operation of thistype of apparatus, fresh methyl chloride is introduced through inlet 31into the bottom of tubular reaction chamber 32 of unit No. l. Thegaseous products from the reaction chamber are separated from most ofthe silicon in the separatory chamber 33 and then enter cycloneseparator 34 where substantial part of the remaining powder entrained inthe gas drops into receiver 35. The fine powder still entrained in thereaction products is removed by filter 36 before the products entercondenser 31 which is operated at a temperature suitable for condensingand separating the methylchlorosilanes and other high boiling productsfrom the unreacted methyl chloride. The condensate collects in receiver38 while the uncondensed methyl chloride flows to the bottom of unit No.2 through pipe 39 provided with a valve 40 for controlling the flow.

The silicon powder collecting in header 33 flows into cooling tube llprovided with control valve 42. The operation and construction of thisportion of unit 1 are similar to the corresponding portion of theapparatus shown in Fig. 1.

Partially used silicon powder is continuously or intermittently purgedfrom header 33 through conduit 43 provided with control valve 44 and thepurged powder is replaced by fresh silicon powder introduced throughpipe 45. The purged powder is carried through the conduit by means ofpart of the reaction products formed in unit No. 1. This mixture ofreaction products and powder is combined with the silicon powdercollecting in receiver 35 and purged therefrom through pipe 46 by meansof a stream of methyl chloride or other suitable gas introduced throughpipe 41 and is introduced into separatory chamber 48 of unit No. 2.Valve 48 in pipe 46 regulates the flow or powder from the separator.

The structure and operation or the unit No. 2 is substantially the sameas unit No. 1. Fresh methyl chloride is added to the uncondensed methylchloride from unit No. 1 through pipe II and the spent powder isperiodically or continually purged from the lower end of cooling tube IIthrough line 52 at a rate sufllcient to compensate for the powderintroduced into unit No. 2 through conduit 43.

The reaction products formed in reactor II or entering unit No. 2 fromconduit 43 leave the separatory chamber of unit No. 2 and flowsuccessively to cyclone separator 64, filter 55, and condenser -58 whichis operated at a temperature sufliciently low to totally condense all ofthe reaction products and the unreacted methyl chloride. The condensatefrom receiver Bl may then go to a stripping column from which methylchloride is taken as overhead product to he eventually recirculated tothe reactors. The silicon powder removed by separator 54 is collected inreceiver 58.

Due to the rapid circulation of powder within the apparatus, any powderpurged from either unit possesses the same degree or conversion andcondition as powder reacting within the unit.,

inasmuch as the reactivity of all types or powoered silicon, siliconmixtures, alloys, etc., appears to decrease as the per cent 01 theoriginal silicon converted increases, the production capacity of anyunit decreases as the average per cent conversion or the silicon powderwithin the unit increases. In order to operate a single unitcontinuously, it is desirable to bleed of! reacted powder eithercontinuously or intermittently at a point in the reactor sufficientlyfar removed i'rom the point or introduction or fresh powder so that thelatter has time to become thoroughly mixed with the reactor contents.Under such circumstances it is necessary to strike a balance between thedesirability of high production capacity and high conversion of siliconand there will be an optimum average per cent conversion or silicon atwhich it will pay to operate a single unit oiany given volume. Byoperating several units in series, the first unit will operate morecmciently than each succeeding unit in which a silicon powder 01' ahigher average per cent conversion is used. The last unit in the serieswill operate with the least reactive silicon, and socalled spent powdermay. be drawn oil from this unit. huch operation is, on the powder side,equivalent to stepwise operation and results in an overall operation ata higher average production rate with a higher average conversion ofsilicon. The number or units which can be economically operated in sucha cascade arrangement will depend upon a balance of fixed charges andoperating costs. In the two stage reactor system shown in Fig. 2, thecondenser 31 separates reaction products from unreacted methyl chlorideand hence increases the eflective partial pressure of methyl chloride inunit No. 2 over the value which would result if the entire gaseouseifluent from No. 12 were to be fed directly to the bottom of unit No.

The reactors need not take the exact form illustrated in Figures 1 and2. The same general principle is embodied in the modiflcationillustratedin Fig. 3. In this modification, the reactor consists of an enlargedcylindrical vessel 60 in which mixing and agitation of gas and powder ismade suificiently violent that temperature gradlents are negligible bothlongitudinally and laterally. The heat or reaction is absorbed by thecold powder nowing to reactor to irom cooler ii. The cold powder may beintroduced either into the side or the reactor or into the bottomthereof through distribution plate 62. Methyl chloride is introducedthrough pipe 63. Even though the cold powder may enter the reactionchamber at a temperature I81 below that prevailing throughout thechamber, mixing of the fresh fluidized powder with that already in thevessel is so enective that the fresh powder is quickly heated to chambertemperature, the heat required for this purpose being abstracted fromthe rest of the powder, thereby providing the desired cooling enect. Ifdesired liquid methyl chloride, liquid methylchlorosilanes, or any othersuitable liquid may be imected through pipe 64 into the stream or powdernowing through the cooler and use thereby made of its latent heat inabsorbing part 01' the heat of reaction. Water is an example or anunsuitable liquid Ior this purpose smce it will react with anymethylchlorosnane vapors present. Hot fluidized powder and gaseousreaction products rlow from the chamber w to cyclone separator where thema or pormon 01 entrained powder 18 removed and dropped into receivinghopper So from which it nows through conduit in to cooler iii and backto reactor w. n necessary, a nuidizing gas may be introduced intoconduit 81 through lines 61'. Final traces or powder are removed Iromthe reaction products in iilter 68. If necessary, the products may alsobe passed through an electrostatic precipitator (not shown) beioreentering condenser as. it may also be desirable in some cases toprecondense a portion of the vapors in order to wet, and therefore aidin the precipitation of, any powder still uncollected at this point. Itis also possible to scrub the gases at this point with total condensateor any other suitable liquid to eii'ect final removal of powder. Thesystem preferably is operated under such a pressure and condenser 69 atsuch a temperature that total condensation of reaction products andunreacted methyl chloride takes place in the condenser. Non-cohdensiblesare exhausted from the condenser through line 10. The condensatecollected in receiver Il may be treated in a stripping column where theunreacted methyl chloride is removed and returned to the system. Freshsilicon powder is charged to the system through line I2 and spent powderdischarged from the system through l3. Like the previous modifications,this reactor may be operated either semi-batchwise or continuously. Insemi-batchwise operation the system is charged with a suitable amount ofpowdered silicon or a powdered mixture of silicon and a catalyst,brought up to temperature, and placed on stream with a hydrocarbonhalide. As the mass of solid silicon powder decreases, additionalsilicon powder is introduced at appropriate intervals. When thereactivity of the powder within the system reaches an uneconomically lowlevel, the entire contents of the system are discharged and the cyclerepeated. It is also possible to charge this once reacted powder to asecond unit in accordance with the principle used with the modificationof Fig. 2 where its effective reactivity may be increased by treatmentwith methyl chloride under more drastic conditions of temperature (andpressure if the second unit is operated independently at a higherpressure) resulting in a further conversion of the silicon tomethylchlorosilanes. Ordinarily the reaction products from such asecondary treatment will contain a large quantity ortrichloromonomethylsilane and relatively smaller quantities ofdimethyldichlorosilane.

In continuous operation the system is charged with powder, placed onstream with methyl chloride, and the powder within the system allowed toreach a certain optimum level of conversion at which time fresh powderis continuously charged into the system and spent powder is continuouslyremoved. It is also possible to charge fresh powder intermittently andto purge spent powder intermittently. The disadvantages of both thecontinuous and intermittent systems may be overcome by operating two ormore reactors of the Fig. 3 type in cascade arrangement as described inconnection with the apparatus oi Fig. 2.

The reaction between a hydrocarbon halide such as methylchloride andsilicon is believed to involve (1) diffusion of the reactant gas up tothe active surface; (2) chemical reaction on the surface and perhaps tosome extent in the gas phase in the immediate vicinity of the surface,and (3) diffusion of reaction products away from the surface. Dependingon the degree of adsorption of any specific reaction products on thesilicon surface, it may be advantageous to subject the circulatingpowder to thorough purging at an appropriate point within its cycle byblasting it with methyl chloride from high velocity jets. The purgingmay be done. for example, either at the entrance or exit to the coolingchamber.

In the modification illustrated in Figure 4 the silicon powder is drawnoil from the bottom of the reactor for circulation to the cooler. Asillustrated. this modification comprises an enlarged cylindricalreaction vessel 8| from which the silicon powder is drawn through line82 to a cooler 83 from which it flows back into the reactor 8| eitherthrough a centrally located distributor plate 84 or into the top of thereactor through conduit 85. Fresh methyl chloride, which fluidizes andcirculates the silicon powder, is introduced into the system between thereactor and the cooler through pipe 88 while fresh silicon powder isintroduced directly into the reactor through inlet 81 and spent orpartially reacted powder removed from the system through outlet 88located near the inlet end of cooler 83. No condensation of the reactionproducts adsorbed on the circulating silicon powder takes place in thecooler because of the fact that the partial pressure of these reactionproducts is small due to dilution thereof with fresh methyl chlorideintroduced into the system ahead of the cooling chamber. The reactionproducts are removed from the reactor through conduit 88 and are carriedthrough cyclone separator 88 where most of the silicon powder isseparated from the gaseous reaction products. The silicon powdercollects in hopper 8i and may be either removed from the system throughpi e 92 or returned to the reactor through conduit 83. If desired.fluidizing gases such as methyl chloride. hydrogen. and nitro en may beintroduced at various points to aid in the circulation of the siliconpowder. In the apparatus shown in Figure 4 two such points are indicatedby numeral 9|. The remaining portion of this apparatus compris ng filter95. condenser 86. receiver 91, and exhaust 98 operates in substantiallythe same manner as the corresponding portion of the apparatus disclosedin Fig. 3.

The bottom drawoi! of powder from the hopperlike bottom of reactor 8ifacilitates the circulation of large quantities of powder relative tothe methyl chloride being used. It will be apparent that it is possibleto operate this modification semibatchwise by the method 01 continuousor intermittent charge or discharge, or a pinrality of such units may beoperated on the dual or multiple cascade principle referred tohereinbefore.

Certain types of contact masses comprising silicon and a metal or metaloxide catalyst may profitably be subjected to a pretreatment whichrenders them more active toward a hydrocarbon halide such as methylchloride. Depending on the particular silicon-catalyst combinationemployed, such treatments may comprise controlled oxidation. with air.steam, carbon dioxide, or other suitable oxidizing gas, chlorinationwith chlorine gas, treatment with hydrogen chloride gas, reduction withhydrogen. or special treatment with some other suitable gas or gases.Such treatment may be conducted advantageously in apparatus operatingeither as a separate unit or in continuous or intermittent connectionwith a reactor in which methyl chloride is contacted with silicon.Partially converted silicon powder of lowered reactivity may frequentlbe reactivated by treatment with hydrogen gas, chlorine gas, hydrogenchloride gas or hydrogen fluoride gas, or some other suitable gas andsuch a reactivation treatment may be conducted advantageously inapparatus operating either as a sepa rate unit or in continuous orintermittent connection with the reactor in which methyl chloride iscontacted with silicon.

A method 01 pretreating and reactivating silicon powder compositions andapparatus suitable for carrying out the method is illustrated in Fi ure5. Three reaction vessels I8I, I82, and I83 are illustrated. Thesereactors may be operated as a continuous or intermittent flow battery,For example, a copper-silicon sintered powder or alloy may be introducedinto reactor I8I through inlet I84 and be subjected there to acontrolled oxidation with air introduced into the bottom of the reactorthrough pipe I85. An suitable heating means (not shown) may be used toheat the contents of the oxidation reactor I 8i. The oxygen-treatedpowder is removed through pipe I86 and is carried thereby to a cycloneseparator I81 where it is separated from the treating gas and drops intohopper I88. The treating gas is exhausted in the cyclone separatorthrough pipe I89 while the powder is discharged from hopper I88 throughpipe II8. All or part of the powder may be recirculated to the reactionchamber I8l through pipe III provided with control or throttle valve 1I2 or part or all of the powder may be intermittently or continuouslycarried to methyl chloride reactor I82 through pipe "3 provided with thethrottle or control valve Ill. An inlet H5 for methyl chloride gas isprovided in conduit H3 between the control valve and reactor I82.Reaction products from reactor I82 along with the silicon powder, andcatalyst, if such is present, pass from reactor I82 through conduit III;to cyclone separator Ill. The reaction products are conveyed throughconduit H8 to a condenser IIS and are thereafter handled in the mannerdescribed in connection with apparatus shown in Figs. 1, 2. 3. and 4.Part or all of the silicon powder collecting in hopper I28 below theseparator II! is either continuously or intermittently recirculatedthrough conduit I2I and I22 toreactorlllorcmductedthrmhplpelllandilltothethirdreactionchamber ill. Numeral ill indicates adrawoiilineforremovingpowder V silicon powderin separator I28 are conductedthroughpipelfitoacondenserlllwhereany condensible materials are removedfrom the treatinggasandarecollectedinreceiver Ill.

I'heuncondensedhydrocarbonhalidrfmmcondenserilimaybereturnedtoreactor'llithroueh conduit llI.

Whilewehaveshownanddescrlbedparticular embodiments of our invention. itwill be obvious to those skilled in the art t at changes and modiflcstons may be made without departing from the invention in its broader asects. We. therefore.aimintheappendedclaimstoeoverall such changes andmodiflcations as fall within the true s irit and scone oi the invention.

Whatweclabnssnewanddesiretosecureby Letters Patent of the United Statesis:

1. The method of pre aring on organo-silicon compound which com risesintroducing a nowderedmixtureoi'siliconandametalcatalyst into a hotreaction zone. and fluidiaing thepowderinthereactionzonewithahydrocarboncompoundcapableofreacflngwiththesilioontoform an organo-silicon compound.

2. The method of preparing organo-silicon halides which comprisesintroducing a mixtme of siliconpowderand apowderedmetal catalystinto areaction zone maintained at an elevated temperature. fluidixing saidpowder mixture in said zonetoabulkdensityoffrom3to4opoimds oercubicfootbymeansofagaseoushydrocarbon halide. separating the reactionproducts of said hydrocarbon halide and silicon from the mixture ofpowdered metal catalyst and unreaci'ed silicon owder. cooling theunreacted powder andretumingthecoolednowdertothereaction zone in aquantity suiflcient to maintain said zone at the desired reactiontemperatures.

3. The method of producing organo-silicon halides which com risesfluidizing a powdered mixture oi'silicon and a metal catalyst by meansof a hydrocarbon halide. continuously passing said fluidized mixturethrough a reaction zone held at an elevated temperature sufllcient tocause a reaction between the silicon component of said mixture and thehydrocarbon halide. separating the unreacted powder mixture from theproducts of reaction. cooling the separated powder and returning saidcooled powder to the reaction zone in a quantity suiilcient to absorbthe heat of reaction evolved therein.

4. The method which comprises introducingafluidizedmixtureofmethylchlorideandapowdered mixture of copper andsilicon into a reac- 'l'hereactivatedporvderisseparatedfromasaaasrflonsoneoperaflngatatemperatureotabout 330-370 6., separating thereaction products and unreacted methyl chloride from the powderedmixture of copper and silicon, removing the separated powdered mixtureof copper and silicon from the reaction zone, coolingthe powderedmixture by contact with a. liquid methylchlorosilane and returning thecooled powdered mixture to the reaction zone along with fresh methylchloride.

5. The method which comprises passing a fluidized mixture of silicon andcopper powder and a gaseous hydrocarbon halide upwardly through arestricted reaction zone maintained at elevated temperatures, separatingthe unreacted powder from the gaseous products of reaction, passing theseparated powder downwardly through a restricted cooling zone,introducing into the powder passing through the cooling zone a gascompatible with the reaction between the silicon component thereof andthe hydrocarbon halide, and returning the fluidized cooled powder to thereaction zone at a rate sumcient to maintain thepowder in the reactionzone at the desired reaction temperatures.

6. The method which comprises maintaining a continuous circulation of apowdered mixture comprising silicon powder and a powdered metal catalystin a closed path upwardly through a hot reaction zone and downwardlythrough a cooling zone by introducing sumcient methyl chloride into thepowder as it enters the reaction zone to lower the bulk density thereoibelow the bulk density of the powder contained in the cooling zone,separating the reaction products and unreacted methyl chloride from theunreacted powder before said powder passes into the cooling zone andcontacting said powder in the cooling zone with a liquidmethylchlorosilane.

I. The method which comprises circulating a mixture of a powdered metalcatalyst and silicon powder through a. hot reaction zone and a coolingzone by fluid dynamic means. contacting the powder with a hydrocarbonhalide in the reaction zone, purging a portion of the unreacted powder.gaseous reaction products and unreacted,

hydrocarbon halide from the reaction zone. separating the reactionproducts and hydrocarbon halide from the purg d powder. circulating theseparated powder through a second cooling zone and reacflon zone andcontacting fresh hydrocarbon halide therewith in said last mentionedreactionzone. A

8. The method which comprises continuously circulating a fluidizedpowdered mixture of copper and silicon powder upwardly through a hotreaction zone and downwardly through a cooling zone, causing ahydrocarbon halide to react with the silicon component in the reactionzone. purging a portion of the unreacted powder, gaseous reactionproducts and unreacted hydrocarbon halide from the reaction zone and.replacing the purged powder with fresh powder, separating the remainingunreacted hydrocarbon halide from the remaining gaseous reactionproducts, inf-roducing a mixture of said unreacted hydrocarbon halideand fresh hydrocarbon halide into a second hot reaction zone, separatingthe purged powder from the purged reaction products and circulating aidpurged powder through a cooling zone and through said second reactionzone in contact with the mixture of unreacted hydrocarbon halide andfresh hydrocarbon halide.

9. The method of producing methyl silicon halides from a powderedsilicon-copper mixture and methyl chloride which comprises passingmethyl chloride upwardly through a mass of heated powderedsilicon-copper mixture at a rate suflicient to fluidize the powder,removing a portion of the powder from said mass, cooling said portionand adding the cooled powder to the mass of heated powder at a ratesufficient to absorb the heat of reaction.

10. The method of preparing organo-silicon halides by reacting ahydrocarbon halide with powdered silicon-copper mixture which comprisespassing a gaseous hydrocarbon halide upwardly through a mass of a hotpowdered silicon-copper mixture in a reaction zone at a rate suflicientto fluidize the powder to a bulk density of from 3 to 40 pounds percubic foot so as to maintain a flow or powder upwardly through saidreaction zone at a velocity less than the velocity of the hydrocarbonhalide, withdrawing hot powder from the upper part, of the reaction zoneand replacing the powder so withdrawn with relatively cool powderintroduced into the lower part of the reaction zone.

11. The method which comprises circulating a fluidized mixture ofpowdered material comprising a powdered silicon and a powdered metalcatalyst in a closed path, treating said powder in one portion of saidcycle with a gas capable of increasing the reactivity of said materialtowards a hydrocarbon halide, withdrawing the treated powder from saidcycle and introducing said powder along with a gaseous hydrocarbonhalide into a hot reaction zone, separating the reaction products fromthe unreacted powder, cooling the unreacted powder, recirculating atleast a portion of the cooled powder to the reaction zone, removing aportion of the cooled powder, treating said powder with a reactivatinggas and returning the reactivated powder to the reaction zone.

CHARLES E. REED. JEROME T. COE.

